The present invention relates to an electrical connector for connecting two circuit boards.
Patent Reference has disclosed a conventional electrical connector. The conventional electrical connector includes a plug connector with a substantially rectangular shape disposed on one circuit board and a receptacle connector disposed on another circuit board. The receptacle connector has a recess portion for receiving a fitting portion of the plug connector through an opening portion thereof when the plug connector is connected to the receptacle connector.
Patent Reference Japanese Patent Publication No. 2007-141586
In the conventional electrical connector, the plug connector includes a housing, and a plurality of retaining grooves is formed in a pair of opposing outer side surfaces of the housing for retaining a plurality of terminals (contacts). The retaining grooves extend in a direction that the plug connector is connected to the receptacle connector (a vertical direction). The terminals with a straight shape are fitted in the retaining grooves from below, and portions of the terminals are exposed as contact surfaces.
In the conventional electrical connector, the plug connector includes retaining grooves extending in the vertical direction and formed in an inner surface of the recess portion facing the outer side surfaces of the housing for retaining mating terminals (mating contacts) when the plug connector is inserted into the recess portion of the receptacle connector. The mating terminals extend in the vertical direction, and have lower end portions (end portions near the opening portion of the recess portion) curved in a U character shape in the recess portion. A contact portion is formed at a distal end portion of each of the curved portions for elastically contacting with the contact surface of each of the terminals of the plug connector.
In the conventional electrical connector disclosed in Patent Reference, the plug connector has the terminals tightly fitted in the retaining grooves such that the terminals do not closely contact with surfaces of the retaining grooves in a longitudinal direction (a fitting direction) thereof over an entire range, thereby forming a gap where the terminals partially contact with the retaining grooves. In other words, an air layer may be formed between the terminals and the surfaces of the retaining grooves along a direction that the terminals are arranged.
Further, when some of the terminals are fitted in the retaining grooves in an inclined state relative to the vertical direction due to a dimensional variance, a size of the air layer formed in the retaining grooves may vary. In particular, when the terminals and the retaining grooves have a relatively large size in the vertical direction, the terminals tend to be fitted in the retaining grooves in a state shifted from a regular state, thereby increasing a variance of the air layer.
Recently, there has been a strong demand for reducing a size of an electrical connector. Accordingly, a connector having a small distance (pitch) between terminals has been preferably developed. When such a connector is used for transmitting a high frequency signal, it is necessary to adjust an impedance of each of the terminals. That is, it is necessary to adjust the impedance of each of the terminals at a same level.
In general, an impedance of a terminal depends on a dielectric constant of an insulating member or an air layer near the terminal. In other words, an impedance of a terminal greatly depends on a size of the insulating member or a state of the air layer along a direction that the terminal is arranged. Accordingly, in order to adjust the impedance of each of the terminals at a same level, it is necessary to arrange all of the terminals in a same condition including the state of the air layer formed between the terminals arranged next to each other.
In the conventional electrical connector disclosed in Patent Reference, when the air layer has a various size along the direction that the terminals are arranged, the impedance of each of the terminals may vary, thereby making it difficult to adjust the impedance of each of the terminals at the same level.
In view of the problems described above, an object of the present invention is to provide an electrical connector capable of reducing a variance in a dielectric constant between terminals, thereby making it possible to easily adjust an impedance of each of the terminals at a same level.
Further objects and advantages of the invention will be apparent from the following description of the invention.